Just cleaning the muck off the top of my oil tank so I moved the ECU out if the way only to discover this rather complicated looking grey connector . There's nothing inside it and it doesn't connect to anything . It has just one red wire going into it . Any answers will be gratefully received.

 

That could be the resister for your fuel gage light. If not I don't know.

 

Resistor pack will have at least 2 wires going to it but I still can't help with what you have there.

 

Well there it is next to the fuel sensor but still don't know



.

 

If you open it up , it's just empty . It's got to be for adding some auxiliary equipment but why the one red wire ? Whatever it is it would have to be earthed and without a switch in the circuit it would be functioning at all times . Further research is called for .

 

Right , sorted . It's called the B+ connector and it is intended for connecting auxiliary equipment as I had previously suggested . There are dozens of references to it with full explanations to be found right here on this very forum . It isn't exclusive to Sportsters either.

 

Be mindful when connecting accessories to the B+ (battery positive) connector. Even though the connector is protected by the 30 amp maxi fuse, the connector is rated @ 9 amps max, and will melt long before blowing the maxi fuse if overloaded.

 

Exactly, make sure you fuse whatever you connect after this connector. I would imagine 30 amps would easily melt the insulation off that tiny wire.